Role of IL-10 in a neonatal mouse listeriosis model

This study was undertaken to test the hypothesis that altered IL-10 product ion plays a role in the increased susceptibility of neonates to listeriosis . Plasma IL-10 levels were measured in neonatal and adult mice at various t imes after infection with Listeria monocytogenes, Relative to adults, neona tal mice had markedly increased IL-10 levels early in the course of infecti on with Listeria using a 90% lethal dose. Higher neonatal IL-10 responses w ere also observed after injecting adults and pups with equal doses of kille d organisms. Splenic macrophages from neonates produced higher IL-10 levels than those of adults after in vitro stimulation with killed bacteria, conf irming in vivo observations. Moreover, IL-10 blockade had differential effe cts in neonates and adults infected with live Listeria, In adult mice, anti -IL-10 Abs decreased bacterial burden early in the course of infection, but were no longer effective at 6 days or later after challenge, In the pups, however, the same treatment had beneficial effects both early and late duri ng infection and resulted in increased survival, Collectively, our data sug gest that an overproduction of IL-10 by macrophages may at least partially explain the increased susceptibility of neonates to listeriosis, and provid e further evidence that cytokine production is different in adults and neon ates.